This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 34 989.7, filed on Jul. 19, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a drive or operating mechanism for opening and closing the flap door or doors of the landing gear bay of an aircraft.
The landing gear of large transport aircraft are typically retractable into a landing gear bay or well, and the opening of this landing gear bay is then covered by a flap door arrangement that may include one or more rather large one-piece or multi-component doors. Due to the required light-weight construction, the rather large door panels generally do not have a very high twisting stiffness, so that special considerations apply for the design of a drive or operating mechanism for opening and closing these doors. Namely, if the drive mechanism is only coupled to one side of the door, then the door will have a substantial tendency to twist or bend, especially while opening and closing due to the non-symmetrical application of force. Such twisting or bending of the door can lead to temporary or permanent malfunctions, mis-alignments, jamming, and the like.
For this reason, it has been necessary to apply the opening and closing force to each individual bay door in a symmetrical arrangement, i.e. at a location at the center of the door or the center of the longitudinal edge of the door. To achieve this, various combinations of actuators such as hydraulic motors or jacks have been conventionally installed directly in the landing gear bay, with further transmission arrangements connected to the bay door or doors. Alternatively, the drive is supported on an additional mounting structure at the center of the bay door. As a further possible alternative, two separate, yet synchronized drives are respectively arranged at the two sides of each individual bay door, to apply balanced and synchronized opening and closing forces to both sides of the door so as to avoid bending or twisting thereof.
Moreover, especially in large transport aircraft, it is typical to cover the horizontal opening of the landing gear bay using a plurality of flap doors or door components that cooperate with each other. In this case, each individual door is respectively equipped with its own separate drive for operating this door.
All of the above mentioned conventionally known arrangements suffer serious disadvantages due to their rather complicated and thus sensitive and not particularly robust structures. Namely, the complicated arrangements suffer a rather high rate of operating problems, with a corresponding high requirement for inspection, maintenance and repair in order to achieve a reliable functioning of the landing gear bay doors. Moreover, efforts to reduce the degree of twisting or bending of large bay doors by instead providing a greater number of smaller bay doors, give rise to aerodynamic penalties, because the respective edges of the adjoining bay doors cause an aerodynamic resistance and have other undesirable effects on the aerodynamic flow conditions along the fuselage in the bay door area. Thus, for aerodynamic reasons, a single or integral bay door is preferred. On the other hand, as mentioned above, such large single or integral bay doors suffer the problem of a relatively low twisting stiffness, which therefore require special considerations in the design and arrangement of the drive mechanism.
It is further desirable to provide only a single door drive mechanism that applies the drive force symmetrically and particularly in a centered manner to the respective bay door, rather than providing two synchronized drives at opposite side edges of the door, for the purposes of saving weight, cost, and complexity. On the other hand, such a centered drive arrangement involves the drive itself or transmission or coupling components being located in an area of the landing gear bay that is generally xe2x80x9cin the wayxe2x80x9d or a hindrance for other components and functions, as well as being exposed to damage by any foreign objects may enter the landing gear bay from the outside when the bay doors are open.
In view of the above, it is an object of the invention to provide a simple, yet robust drive mechanism for aircraft landing gear bay doors, especially in connection with a landing gear bay door having the lowest possible number of individual parts for covering the open area of the landing gear bay. It is a further object of the invention to provide an asymmetrical arrangement of a drive motor, actuator, or other drive prime mover, while still applying the drive force to the individual bay door in an advantageous manner to avoid twisting or bending of the door during its operation. Another object of the invention is to avoid the arrangement of the drive and transmission components in the open area of the landing gear bay to thereby avoid the danger of damage to such components by foreign bodies that might enter the landing gear bay when the bay doors are open during take-off and landing of the aircraft. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in an operable landing gear bay door arrangement for an aircraft, wherein a door flap is supported on a pivot support shaft that is hollow along at least a partial length thereof, and preferably along the entire length thereof, and that in turn is pivotably supported in two bearings. A drive shaft extends coaxially in the hollow interior of the pivot support shaft, and is connected to the pivot support shaft by a torque-transmitting connection near the longitudinal center thereof. The drive shaft is connected to a drive such as a hydraulic motor, an electric motor, a hydraulic jack, a screw jack, or any other known type of actuator, either directly or through a gear drive, a transmission linkage, or a drive lever, or the like, so as to exert a torsional moment onto the drive shaft. This torsional moment is transmitted from the drive shaft to the pivot support shaft through the torque-transmitting connection therebetween. Along the length of the drive shaft extending coaxially in the hollow interior of the pivot support shaft, the drive shaft is not connected to the pivot support shaft, but rather is freely twistable, pivotable, and flexible therein to a limited extent, because of the provision of an annular clearance gap therebetween.
In the above manner, while the drive itself is arranged asymmetrically to one side of the bay door, the drive force is applied to the bay door at a generally centered location, so as to have a symmetrical influence on the door and thereby avoid twisting or bending thereof. The force-transmitting connection between the drive shaft and the pivot support shaft can be carried out in a positive form-locking manner or in a force-locking manner such as by a frictional or press-fit connection. The preferred connection is a form-locking connection, and may further be secured with a pin, screw, bolt or rivet.